Computer Networks — DU B. Sc. (Hons) Electronics Previous Year Question Papers

2. There are seven questions in all, out of which you have to attempt five questions. (a) Categorize the Star, Bus and Ring topologies in terms of line configuration. Given an input data stream as 010111. Sketch the following encoding schemes (b) What is CSMA? Discuss the three persistence methods. (c) Answer each of the following briefly : (i) Give one similarity and one difterence between OSI and TCP/IP reference (i) The following character encoding is used in a data link protocol Show the bit sequence transmitted in binary for the four-character frame: A B ESC FLAG using the framing method of "Flag Bytes with byte Stuffing" (iii) Show the original (unabbreviated form of the following address (iv) Write the following in slash notation (/n) (v) Find the net id and the host id of the following : (vi) What port numbers are used by HTTP and FTP respectively? (a) Draw a schematic comparing different layers of the TCP/IP Model with the OSI Model. How are the Network Layer and Transport Layer different in two models? (b) What is signal impairment when it travels through transmission media and what are its causes? We need to send 260 kbps over a noise less channel with bandwidth of 20kHz. How many signal levels do we need? (c) Differentiate between Repeaters, Hubs, Switches and Bridges. With respect to ISO-OSI model, name the layers in which these devices operate. (a) Briefly describe the services provided by the DLL. Distinguish between Bit and Byte stuffing. (b) A bit stream 10011101 is to be transmitted using the CRC method. The generator polynomial is x3+1. Show the actual bit-string which is transmitted after encoding. Suppose the third bit from the left is inverted during transmission. Determine whether this error is detected at the receiver end or not. (c) How is guided media different form unguided media? Name the three main classes of guided media. What is the position of the transmission media in the OSI or the Internet Model? (a) What is the difference between a port address, a logical address, a physical address and a specific address? (b) Compare and Contrast the Go-Back-N ARQ with Selective-Repeat ARQ. (c) Define Controlled Access and discuss briefly the three protocols in this category. (a) A block of addresses is granted to a small organization. One of the addresses is 198.16.37.39/ 28. What are the first address and the last address in the block? Also find the total number of addresses in the block. (b) What is the difference between open loop congestion control and closed loop congestion control? Explain one mechanism of each kind. (c) What is ARP and RARP? Explain. (a) Draw a labeled TCP Segment Header mentioning the bit numbers for each field. Explain the flags/ bits of the control field. (b) What is UDP and how is it different from TCP? (c) What is FTP? Compare it with HTTP. (a) Compare and contrast the fields in the main headers of IPv4 and IPv6. Make a table that shows the presence or absence of each field.